London: Mothers who have high levels of n-6 polyunsaturated fatty acids (PUFAs) - generally found in cooking oils and nuts - during pregnancy have fatter children, researchers say.

The study, carried out by the Medical Research Council (MRC) Lifecourse Epidemiology Unit, University of Southampton, assessed the fat and muscle mass of 293 boys and girls at four and six years, who are part of the Southampton Women's Survey (SWS), a large prospective mother-offspring cohort.

Their assessments were compared to the concentrations of PUFAs which were measured in blood samples collected from their mothers during pregnancy.

The study found that children who were born to mothers who had had greater levels of n-6 PUFAs during pregnancy had greater fat mass.

Dr Nicholas Harvey, Senior Lecturer at the MRC Lifecourse Epidemiology Unit, University of Southampton, who led the research with Dr Rebecca Moon, Clinical Research Fellow, comments: "These results suggest that alterations to maternal diet during pregnancy to reduce n-6 PUFAs intake might have a beneficial effect on the body composition of the developing child."

Results from the study also showed weaker associations between a mother's levels of n-3 PUFAs, more commonly known as omega 3 and found in fish oil, and muscle mass in their offspring - the higher the level of n-3 the less fat and more muscle and bone in the baby.

This could suggest that a pregnancy supplementation strategy would be beneficial. However Dr Moon says: "n-6 and n-3 PUFAs seem to act in opposite directions on fat mass; previous trials have attempted to use n-3 supplementation to reduce fat mass, but our results suggest that such an approach might work best when combined with a reduction in dietary n-6 intake."

The study has been published in the January edition of Journal of Clinical Endocrinology and Metabolism.